functions – How to show a conditional with more options (Checkout)

How to show a conditional with more options if I choose the first option (this works in checkout)

enter image description here

function kia_filter_checkout_fields($fields){
    $fields('extra_fields') = array(
            'some_field' => array(
                'label' => __( Options' ),
                'type' => 'radio',
                'options' => array( 'Books' => __( 'Books' ), 'Citys' => __( 'Citys' )),
                "class"         => array("columns"),
                'required'      => true,
                )
            );

    return $fields;
}
add_filter( 'woocommerce_checkout_fields', 'kia_filter_checkout_fields' );